Tag Archives: dinosaur

Why dinosaurs are not extinct

In the twenty plus years I have been involved in paleontology I have been witness to a revolution within science. The revolution has been quiet, not noticed by most of the public. Like any good revolution, the battles of this revolution took place between two camps, the “traditionalists” and the “radicals” who were out to change things. And this shift is illustrative of how science as a whole moves from one way of understanding to a brand new way of looking at the world. It is, in fact, a paradigm shift that has profoundly changed biology and paleontology forever.

At issue is how we explore and classify the relationships of all living things. The traditional view, the one that I was taught as a young student, was the classification of living things into the taxonomy originally begun by Carl Linnaeus. This system started with a group, and then sought to put things into the group. For example, one can make the observation that animals that look like “dogs” could be grouped together, so you would start with the idea of a dog-group and look for animals that should be included.

You might put foxes, wolves, domestic dogs into the group, and call it the dog family. You might also note that “cats” could likewise be grouped, and do the same thing, creating a cat family. In this view, the families were equal in rank—and there could be no overlap. An animal would be included in only one of the equal-ranked families. Any animal was included in only one class, for example Amphibia, Reptilia, Aves, or Mammalia.

The equal-ranked heirarchy of classifications worked well enough when we mainly were concerned with modern animals. Clearly, birds look different than mammals and reptiles, so it seemed evident they belonged in their own class. But this classification scheme, however well it served us as a place to start, is myopic about how evolution actually operates—how organisms actually evolve. This is understandable since it was started 100 years before evolution as a theory was established.

In trying to shoehorn life into the system, we repeatedly ran into problems as we expanded our knowledge of the diversity of living things and our understanding that the history of life is a complex branching bush. We knew that early tetrapods (organisms with four limbs) gave rise to the early amphibians that crawled out on land, and that they in turn evolved into reptiles, mammals and birds. But despite this branching within tetrapods, the class ranks were forced to be exclusive, so somewhere in evolutionary history was an “amphibian” that had to become a “reptile,” and a “reptile” that had to become a “bird.”

The many transitional forms in the fossil record increasing became impossible to classify. These intermediate animals had to be forced into one class or another. Increasingly, it became evident that many times the criteria used to put an organism into one class were the whims of an individual scientist, and another equally qualified expert with different opinions might place the same animal in a different class with equal validity.

The origin of birds was for a long time a great mystery to paleontologists. Birds are a pretty unique and specialized group, and while we knew that they originated from reptiles somehow, exactly how and when was unclear. One early paleontologist noted that dinosaurs had many features in common with birds, but the early concepts of what dinosaurs were like distracted most scientists from comparing them too closely. After all, the common conception of dinosaurs was as big, lumbering, dim-witted, swamp-dwelling beasts. The bird ancestor must have been light, fast moving, and energetic.

However, dinosaur research over the last thirty years has completely changed our view of them. Evidence from many lines, including things like footprints and the cellular structure of the bones, all point to dinosaurs as being very dynamic creatures. With this new view, the notion that birds were linked to dinosaurs became clear too. Now, we have dinosaur fossils with feathers, and birds with teeth and dinosaur tails to attest to their close relationships. In fact, birds are most closely related to the meat-eating raptor-like dinosaurs of Jurassic Park fame.

To go along with the revolution in our view of dinosaurs was that revolution in science that I mentioned above–the emergence of a new way to understand the interrelationships of life on Earth. This new model accommodated the myriad branching events that life actually experienced in order to produce the great variety of living things. So, instead of starting with a conception of the group and looking for members, this new concept looked at the branching patterns evident in life, and then sought to apply names.

Below is an illustration of the branching pattern of selected tetrapods, those vertebrates with four well developed limbs. As the first tetrapods gave rise to new and different groups, the branches split off. An early tetrapod gave rise to amphibians and the other animals above it on the chart (mammals, turtles, etc.). A later tetrapod developed traits related to the production of eggs and young that we recognize as the Amniota. Some of those early amniotes went off on an evolutionary trajectory that we can recognize as being the early mammals, and all the diversity that resulted from them. And so it goes up along the branches.

Branching pattern of the tetrapods, mostly the land vertebrates

We now explore the branches and can apply names to the groups that we find to be meaningful. For example, in the illustration below we can call everything in the box a reptile. Note that it includes things that used to be called reptiles, turtles, lizards, snakes, crocodiles, and dinosaurs, but now also includes birds.

Group that includes all the reptiles

Likewise, if we draw a line around the dinosaurs, they also include the birds. This view of life tells a more complete evolutionary history and retains the branches, letting the animals “fall where they will.” We do not pull birds out of their relationships and give them special consideration. Instead of birds being equal in rank with reptiles, they are included among them. This upsets the tradition that being a bird is somehow equally important to being a reptile, but better reflects the reality of descent, without forcing nature into earlier human conventions of naming and grouping. Of course, birds are a group within their own right, and we could zoom in to explore their branching pattern, but it does not change the group to which they belong.

Group of dinosaurs

This leads to another startling statement. Below I have highlighted the groups that are extant (still around today).

Groups of tetrapods that are alive today (extant)

Because of our grouping scheme, birds are included in the dinosaur group, so dinosaurs are not really extinct! They live among us today flitting about, singing their mating songs in the trees. It is funny how things can change in science. Twenty years ago scientists would have told you the dinosaurs were all extinct, and today we say the opposite. I love scientific progress–it can be so startling.

Spending time in Purgatoire

One of the many places that I have been fortunate to spend time in is Purgatoire. Perhaps not the same thing you are thinking, but I am referring to the Purgatoire River Canyon in southeastern Colorado. Located south of La Junta, this area is an often-overlooked gem. The scenic vistas could be used for your desktop wallpaper!

Purgatoire River Canyon in southeastern Colorado

The many names applied to the region can be confusing. The Purgatoire River has cut a dramatic canyon in this part of the plains, and with the Rocky Mountain Front Range far to the west, it can be almost startling to come upon the deep canyon in an otherwise rolling plains landscape. Anglo settlers bastardized the name of the river, and instead of the eloquent Purgatoire, ended up calling the area Picket Wire, so both names alternately apply.

The area is managed predominately by two federal agencies, the United States Department of Agriculture’s Forest Service and the Department of Defense through the Army. The military uses their lands for maneuver practice, as I understand it, tanks and other mechanized equipment. Some years ago the Army carved off some of their land and gave it to the Forest Service to manage as part of the Comanche National Grassland. The Forest Service land is used for recreation and also the preservation of significant historic and prehistoric resources.

Petroglyph of human and horse figures

Rourke Ranch house in the Purgatoire Canyon

The historic resources include Native American petroglyphs and other archeological sites, early Spanish homestead sites and churches, early American homesteads. The prehistoric resources include dinosaurs and other prehistoric animals, both body fossils and trace fossils. I was very fortunate to have been involved in the documentation of some of the first dinosaur fossils from the region (Schumacher and Liggett 2004).

Dinosaur trace fossils, in particular dinosaur tracks, are well preserved in one section of the Morrison Formation in the bottom of the canyon. These tracks were discovered in 1935 by a young girl as can be seen in this newspaper clipping from the Topeka Capital Journal. However, the tracks are most definitely not those of a Tyrannosaurus rex (mentioned in the clipping) as that beast did not stalk the Earth for at least 90 million years after the track-makers walked here. This track site is the largest continuous track site of dinosaurs known from North America, and contains over 1,400 prints.

Newspaper clipping announcing the discovery of the Purgatoire track site

However, because of the remoteness of the site, scientists turned their attention to other dinosaur tracks found in Texas, and the Colorado tracks were essentially forgotten for many decades. However, a newer generation of scientists have re-examined the track site. Of interest is the fact that the site shows five parallel sauropod tracks, suggesting that at least in this case, the animals walked along together spread out, not walking in a line (Lockley 1991).

There are actually several track layers in the rocks. Also preserved are several three-toed theropod, or meat-eating dinosaur. While it is difficult to exactly match the track to the species of dinosaur that made them, the large sauropod tracks were made by an animal like Apatosaurus (Brontosaurus of old) and the meat-eating tracks are similar to what an Allosaurus would make.

A well-preserved theropod dinosaur track in the Purgatoire Canyon

View of the Purgatoire River track site using low altitude photography

In addition to the tracks, the canyon is also now yielding body fossils of dinosaurs. It is really no surprise since the Morrison Formation is extensively exposed along the river canyons. The Morrison is the name given to a wide-spread formation that is the most prolific producer of Jurassic dinosaurs in North America. The formation outcrops in North Dakota, South Dakota, Montana, Wyoming, Colorado, Oklahoma, Texas, New Mexico, Arizona, Utah, and Idaho. Every Jurassic dinosaur you have ever heard of comes from the Morrison; animals such as Allosaurus, Apatosaurus, Diplodocus, Stegosaurus, and Camarasaurus all come from this formation. (See Formations for information about what that means.)

Stratigraphic section of the Purgatoire River Canyon showing the geologic formations that outcrop

Given the Purgatoire River’s remoteness, and the fact that it was controlled for many years by the Army, few people were able to explore the region until more recent decades. Thus, now it is one of the last areas of the Morrison Formation exposures to be explored. And it is proving to be as rich as expected.

Over the last decade, the Forest Service has been conducting Passport in Time (PIT) programs in the canyons, looking for new dinosaur sites, and excavating sites. Many people, scientists, graduate students, and the lay public have enjoyed excavating dinosaurs in this beautiful and remote canyon. And several significant specimens have come out of the area. The Forest Service has partnered with many museums from the region to study this treasure-trove and to allow people to enjoy this amazing region.

Volunteers excavate dinosaur fossils from the Woody site

Dinosaur vertebra from the Woody Site being prepared at the Sternberg Museum of Natural History

Plastered dinosaur bone being carried out of the LC Site

Volunteers excavate dinosaur bones from the Morrison Formation at the LC site

The Forest Service offers tours of the canyon and track site. If you are interested contact the Forest Service Office at 1420 East 3^rd, La Junta, CO 81050, 719-384-2181. If you plan to visit the area on your own, be aware of a couple of things. You cannot drive into the canyon without prior authorization. You can hike in on your own, but it is several miles in and out, and the summer temperatures can be brutal, so bring plenty of water and plan accordingly.

A large section of Dakota Formation slumping away from the main block provides a dramatic hiking experience

Lockley, M. G. 1991. Tracking Dinosaurs: A New Look at an Ancient World. Cambridge University Press, New York.

Schumacher, B. A., and G. A. Liggett. 2004. The dinosaurs of Picketwire Canyonlands, a glimpse into the Morrison Basin of southeastern Colorado. Journal of Vertebrate Paleontology 24(Supplement to 3):110A. (Poster page 1 and page 2).

Many other dinosaur facts can be found here at Boneblogger. Just search or select the category.

Dinosaurs dragging their bellies—Huh?

Isaac Newton famously wrote in 1676,“If I have seen further it is by standing on the shoulders of Giants.” This gets to the heart of the scientific process—a gradual addition and refinement of human knowledge and understanding of the natural world. But, of course, sometimes even giants had wacky ideas.

The particular “giant” to whom I refer is Charles H. Sternberg, famed fossil collector. Sternberg began collecting fossils when he was seventeen, at a time when it was not exactly commonplace, in about 1867. And he dedicated his life to this unusual pastime, founding a family of fossil collectors when his sons continued the tradition for a second generation. Together, the Sternberg family collected a huge number of fossils for museums and science. There is hardly a major museum in the world that does not have one of their discoveries on display.

Sternberg started his career in the hills of western Kansas, collecting fossil plants from the Dakota Formation. He sent his specimens back to the young Smithsonian Institution, for which he received a letter of acknowledgment that he treasured his whole life. He was bitten by the “fossil bug.”

A rare photograph of Charles Sternberg (right) with his twin brother Edward (left).

By 1875, he enrolled in college where he studied briefly under Benjamin Mudge. Mudge organized a fossil collecting trip for 1876 to collect for O. C. Marsh, the Yale College paleontologist. Sternberg was too late to sign up with Mudge, and bitterly disappointed, and somewhat brazenly, he wrote a letter to Edward D. Cope, Marsh’s rival.

Sternberg wrote, “I put my soul into the letter I wrote him, for this was my last chance. I told him of my love for science, and of my earnest longing to enter the chalk of western Kansas and make a collection of its wonderful fossils, no matter what it might cost me in discomfort and danger. I said, however, that I was too poor to go at my own expense, and asked him to send me three hundred dollars to buy a team of ponies, a wagon, and a camp outfit, and to hire a cook and driver. I sent no recommendations from well-known men as to my honesty or executive ability, mentioning only my work in the Dakota Group.” (Sternberg 1909, pg 33).

Sternberg anxiously awaited a reply, and when he opened Cope’s letter, a draft for $300 fell out, a very significant sum. So began his professional fossil hunting career. Over the years he collected throughout the American and Canadian west. In the twilight of his career he semi-retired to San Diego, and was allowed to use the title of curator at the natural history museum.

Museums and libraries are marvelous places, full of fascinating treasures. It was while reading in the archive at Fort Hays State University’s Forsyth Library that I came across a carefully saved clipping of an article from the Los Angles Time Sunday Magazine from December 20, 1931, titled “The habits of dinosaurs,” written from an interview with the 80 year old fossil collector.

In the article, Sternberg is quoted as giving his vision of the life of some of the dinosaurs that he had collected over the many years. While I recognize that it is not really fair to judge the views of earlier experts, especially with the perspective of almost three quarters of a century of additional knowledge, but it can be damn funny.

Sternberg is quoted as authoritatively saying, “Dinosaurs were lizards. They stood and walked like lizards, not like elephants or rhinos. That is to say, the normal positions of their feet were outside the line of the body, just like the alligators of today, not inside or even with the line of the body, as are the feet of horses, elephants and other mammals. Moreover, the dinosaur, instead of standing up, on straight legs, as usually pictured, bent its legs outward, as do the lizards, and dragged it belly on the ground, again like the alligators, monitors and other large lizards of the present day.”

Dinosaur reconstructions of that period typically showed dinosaurs with spindly, lizard-like limbs, and tails dragging, but with a generally upright posture. Sternberg evidently did not agree, arguing in favor of his views with some odd reasoning.

Citing fossils of preserved dinosaur skin, he said, “Furthermore, the skin on the lower side of the abdomen of this dinosaur was much thinner and more delicate than on other parts of the body. This is further and strong argument for my claim that the dinosaur dragged its belly on the ground, as do the alligators of today, which so protect their vital parts from carnivorous animals…you may be sure that no tender-stomached dinosaur, whether it weighed forty tons or forty pounds, would voluntarily expose its tenderest and most vital parts to attacks by the tyrant dinosaur or any other carnivorous creature by walking erect.”

Illustration from Los Angles Times Sunday Magazine, 1931

Illustration from Los Angles Times Sunday Magazine showing Sternberg's idea of dinosaur stance.

I totally agree. I hate walking around with my “tenderest” parts exposed. The accompanying illustration of Sternberg’s vision of the Mesozoic is hilarious, with giant sauropod (long-necked) dinosaurs hunkered down, presumably guarding soft spots. I am not really sure how Sternberg expected it would work for a forty ton animal to push itself along the ground with its legs sprawled out to the side, much less how it would support its own weight on its chest, but details, details.

Even though the article claims that Sternberg was a “man of facts and not fancies,” he was prone to exuberant musing about the prehistoric beasts he collected. While he could be wacky, we owe a great debt to the entire family for their contributions to science.

Further reading about the Sternberg family:

Everhart, M. Oceans of Kansas website, summary of the work of Charles H. Sternberg.

Everhart, M. J. 2005. Oceans of Kansas: A Natural History of the Western Interior Sea. Indiana University Press, Bloomington.

Liggett, G. A. 2001. Dinosaurus to Dung Beetles: Expeditions Through Time, Guide to the Sternberg Museum of Natural History. Sternberg Museum of Natural History, Hays, Kansas.

Rogers, K. 1991. The Sternberg Fossil Hunters: A Dinosaur Dynasty. Mountain Press Publishing Company, Missoula, Montana.

Sternberg, C. H. 1909. The Life of a Fossil Hunter.

Other interesting dinosaur facts are found here at Boneblogger. Search or select the category for more.

Sternberg, C. H. 1917. Hunting Dinosaurs in the Bad Lands of the Red Deer River Alberta, Canada. Charles H. Sternberg, San Diego.

Feathered dinosaurs may have changed coats

Some of the most exciting finds of the last couple of decades were the discovery of feathered dinosaurs. These fossils mostly have come from fine-grained formations of the Cretaceous Period in China, where feather impressions were preserved along with the bones. Each of these fossils gives us a snapshot image of the body covering sported by that species. Other recent finds have even given us clues to the coloration of the feathers in a few species.

In yet another new find, announced in the April 29 issue of Nature, we learn that the feathery covering may have fundimentally changed over the lifetime of individuals of at least one species. Two small oviraptors in the genus Similicaudipteryx were preserved at different stages of their life history, each showing the pattern of feathers covering the body at different life stages.

Artist reconstruction of a juvenile and adult Similicaudipteryx. Artwork by Xing Lida and Song Qijin

The smaller, juvenile individual had short flight feathers with a “ribbon-like” stem on its forearms, much long feathers on the tail, and a downy covering over the rest of its body. The larger, young adult individual showed a different pattern, with much longer, and more developed flight feathers with a strong central shaft on the forearm. Thus, the flight feathers of the forearm show two very different morphologies at the two life stages. This does not happen in modern birds, where the flight feathers that emerge on the juveniles are the same, only smaller versions of the adult feathers.

There is some debate that this interpretation of the fossils is correct. It could be, argue some paleontologists, that the smaller individual was preserved during a molting phase, with the new feathers only partially emerged from the tube-like sheath that feathers form in. In other words, they suggest that the different morphology is only temporary and an artifact of preservation. The authors of the original paper maintain it is not an artifact based upon the proportions of the feathers. So, we need to keep digging.

It is now accepted that the ancestors of birds were the theropod (meat-eating) dinosaurs. It is clear from these fossils, and many similar ones, that birds inherited their feathers from dinosaurs, and we have greatly expanded our knowledge of feather evolution with the last few years.

Other dinosaur related posts can be found here. Just search or select the category.

SuperCroc at Sternberg

The Sternberg Natural History Museum at Fort Hays State University is featuring a new exhibit, The Science of SuperCroc from now until August 5.

The star of the show is the African crocodilian species Sarcosuchus whose remains have been found in the modern Sahara, in the Elrhaz Formation. This Early Cretaceous (~112 million years ago) crocodile had a long, slender snout with a prominent down-turn or hook at the tip. When fully mature it is estimated to have been between 37-40 feet in length, and weighed as much as 17,000 pounds.

The largest living crocodile is the saltwater croc, and the largest confirmed individual was just over 20 feet in length and weighed a mere 2,600 pounds.

Restoration of Sarcosuchus, the SuperCroc

Sarcosuchus had its eyes placed high upon its skull suggesting that it spent most of its time submerged in the water. Like so many other things in paleontology, the question of what Sarcosuchus may have eaten is not agreed upon by researchers. Some suggested that the size of Sarcosuchus and its overhanging upper jaw made it able to wrestle large prey items, even massive long-necked sauropod dinosaurs. Others point to the slenderness of the muzzle and it not looking stout enough to withstand the forces that would be required to bring down large prey. There were plenty of lobe-finned fish in Sarcosuchus’s environment. I see a fish-eater in this skull myself.

Also on display with the large croc is Suchomimus, a theropod dinosaur whose remains have been found in the same geological formation as Sarcosuchus. Suchomimus, whose name means crocodile mimic, was a forty-foot long beast which also had a long slender muzzle. Its forelimbs were armed with very long sickle-curved claws. This animal is thought to have eaten fish and probably other sorts of meat, but its skull also does not appear equipped for biting and holding very large struggling prey.

SuperCroc Sarcosuchus skeleton at Sternberg Museum

The presence of both of these animals, and many others found with them, show that the Sahara area of today was a lush, swampy habitat in the Early Cretaceous. The effect of climate change and plate movements over millions of years can turn a wet verdant habitat into a harsh, dry desert. My how times change.

Go see SuperCroc at the Sternberg Museum if you have a chance.

Boneblogger: Science and the outdoors

Exploring the natural world